Georgetown University is studying the mechanisms of chromosomal instability in breast cancer, in particular the amplification or mutation of several oncogenes and suppresser genes. They are focused on the role of the myc oncogene in transgenic mouse models as a model system whereby they may study its role in mammary tumorigenesis. The specific aims are to obtain sorted mouse chromosomes from the FVB strain, fluorescently label these chromosomes to establish multicolor FISH spectral karyotyping at Georgetown, and to use this technique to establish the time dependent nature of chromosomal instability induced by the c-myc oncogene in mouse mammary epithelial cells.